building router extension

[durango dude]

I found two nice and flat 3/4" pieces of plywood the other day - and decided it's time to built a router extension on my BT3000.

It looks like the top of my BT is 1.5" --- and I'll need a 1/4" ledge to run into the saw's extended rail.

My big task is to cut a perfectly round 7" circle --- rabetted down by 1/4" for the router.

Help me think this out ---

Supplies needed:

a) Either circle cutting bit for drill press OR a circle cutting tool for a jigsaw
(I'm thinking the drill press approach is more precise)

b) Rabetting bit - to cut out the ledge for the rail --- as well as the ledge for the router base.

Measuring my router - it looks like I want a 6 1/2" circle --- followed by 1/4 ledge - making the final hole 7" in diameter (the router base diameter). Is 1/4" enough? (I might want 6" circle, with 1/2" ledge - which is as small as I can go with my router).

Am I under/over-thinking this?

[Cochese]

I know I'm telling you something you already know, but I'd consider a plate. If you ever have to change routers, you won't compromise what you've built.

[JR]

I know I'm telling you something you already know, but I'd consider a plate. If you ever have to change routers, you won't compromise what you've built.

+1

You'll find a router plate will provide a lot flexibility you didn't know you needed, such as insert rings providing variable opening sizes, easy removal of the router for bit changes, simplified initial installation, etc.

JR

[vaking]

Extension wing for BT is 22+" wide - you need a minimum 12" drill press to drill a whole in the center. Also circle cutting jig for drill press usually does not go to 7" diameter sizes. I would suggest circle cutting jig for the router and a 1/2" straight bit to cut 7" diameter circle in plywood. Circle cutting jig for router is easy to make yourself if you don't have it.
A plate is also is good idea.

[LCHIEN]

a router plate is better but if you want to cut a 7" hole a DIY router circle cutting jig is super easy. Scrap piece of wood and 5 minutes work. Don't need to spend $50 for one. Ask if you don't know how to do one.

[durango dude]

a router plate is better but if you want to cut a 7" hole a DIY router circle cutting jig is super easy. Scrap piece of wood and 5 minutes work. Don't need to spend $50 for one. Ask if you don't know how to do one.

You got me pegged!

Actually - what I was thinking of doing was not using the router hole on my BT --- but building my own table between my rails.

So maybe I cut that circle --- will likely need a rabetting bit since my router plate is not the same depth as my 3/4" thick wood. (dang - drawings would sure make life easier --- wouldn't they?)

I found a circle cutter at Grizzly - for $15. The more expensive thing is the darn rabetting bit set --- which runs $25 on a cheap day. (plus $10 shipping)

(I could use a rabetting bit, anyway)

[Cochese]

If you can make a jig that the router can ride inside of, I'd recommend a pattern bit. It's what I used to make the cutout for my plate.

http://www.rockler.com/product.cfm?page=25160&filter=pattern%20bit

A cutoff piece of a paint pail, or whatever fits your diameter would work for the initial pattern, then remove and go deeper.

[LarryG]

+4 (or whatever we're up to) on buying an insert plate. That said, I'm unable to determine exactly what you're planning.

If you're going to make a custom router base plate that will drop into an opening on your extension table, the plate and the hole don't necessarily have to be round.

You could also cut a relief on the underside of your extension table a little larger than your router base, leaving about 3/8" of thickness on the top layer of plywood. Drill a hole as large as the biggest bit you'll use. Then attach your router base to the underside. In effect, your entire extension table becomes an oversized custom base plate.

[JimD]

The last paragraph of LarryG's post is exactly what I did and recommend. No plates for me. My extension table is mostly 3/4 melamine particle board. It has plywood stiffening ribs. I drilled a hole a little over 3 inches so I could use big panel raising bits and then routed the underside to reduce the thickness to 3/8. I screwed a fixed base for one of my PC690s to it and I have a router table. I have a fence that attaches through t-nuts in the extension table for knobs with studs that go through slots in the fence for adjustment. I have less in this setup than you guys paid for plates. And I do not see the functional advantage of the plates.

Jim

[LCHIEN]

DD,
a 3/8" rabbeting bit (or 1/4" if you prefer) is only $15 or 16 delivered, from www.MLCSWOODWORKING.com, you don't need to buy a full rabbeting bit set.

Alternatively, you can buy the MLCSWOODWORKING 15-bit set that includes the 3/8" rabbet bit for $40, 14 additional bits for only $25 more than the one bit you want.

If you also need a 1/4" x 1" long straight bit to cut the hole, then that set will have one and save you another $8, giving you 13 bits for $17 more.

If you are really on a budget, to cut a stepped hole, you don't need a Rabbet bit, just use a straight bit to cut a partial hole from the top and bottom, with the radius on the top(or bottom) 3/8" more than the other side.

[Ed62]

I'd say Jim's post shows a very workable solution. But if you have a little extra cash to get rid of, I think another plate would be a good way to go simply because you might decide to build a new router table in the future, and that would be an easy way to switch routers. Of course you could always buy the plate at some time in the future if you decide to build again. Another plus for the new plate is that it would make it very easy to lift the router out for cleaning.

Ed

[JR]

The last paragraph of LarryG's post is exactly what I did and recommend. No plates for me. My extension table is mostly 3/4 melamine particle board. It has plywood stiffening ribs. I drilled a hole a little over 3 inches so I could use big panel raising bits and then routed the underside to reduce the thickness to 3/8. I screwed a fixed base for one of my PC690s to it and I have a router table. I have a fence that attaches through t-nuts in the extension table for knobs with studs that go through slots in the fence for adjustment. I have less in this setup than you guys paid for plates. And I do not see the functional advantage of the plates.

Jim

Your post shows that there is no one router setup that's perfect. I also have the fairly comlex Wood Mag fence in my setup. OTOH - I've seen many articles and videos in which professionals set up a very simple and funky router table and fence. To each his own.

I like a plate because of the variable opening size (a 3" hole would be way too wide for much of the work I do). I also like to take the whole assembly out of the table some times, especially when removing the motor for installation in the plunge base and sometimes for bit changes. With a plate the whole shebang just lifts out.

YMMV,
JR

[LCHIEN]

Here's my tutorial on cutting large circles with a router and a (almost free) 5 minute DIY jig.

http://www.bt3central.com/showthread.php?t=54815

[Cochese]

The last paragraph of LarryG's post is exactly what I did and recommend. No plates for me. My extension table is mostly 3/4 melamine particle board. It has plywood stiffening ribs. I drilled a hole a little over 3 inches so I could use big panel raising bits and then routed the underside to reduce the thickness to 3/8. I screwed a fixed base for one of my PC690s to it and I have a router table. I have a fence that attaches through t-nuts in the extension table for knobs with studs that go through slots in the fence for adjustment. I have less in this setup than you guys paid for plates. And I do not see the functional advantage of the plates.

Jim

My plate is 1/4" aluminum, so I have a slight advantage in depth of cut, and I never have to worry compromising the top due to the weight of the router. Those might not be problems for you, but they are problems for some.

Having a plate also allows me to drop in different inserts for dust collection or above table bit changing. The added convenience was well worth the cost of admission.

Also, considering I'm planning my third version of a router table (size issues), I only have to cut the hole for the plate, which is made easier due to the template I have. Any future router additions will all use the exact same cutout due to the standardization of the plate.

YMMV